Analog Sensor Interface for Field Mill Sensors in Atmospheric Applications

Abstract

An overview of the electric field mill sensor specifications in applications related to the measurement of the atmospheric electric field was conducted. The different design approaches of the field mill sensor interface are presented and analyzed, while the sensitivity-related parameters of a field mill are discussed. The design of a non-complex analog sensor interface that can be employed for the measurement of the electric field in both fair and foul weather conditions, such as thunderstorms, is implemented using discrete components for experimental validation and is optimized in an integrated version in terms of noise and power consumption. Advanced noise simulations are conducted in a 180 nm CMOS process (XH018 XFAB). The energy-autonomous operation of the sensor for extended periods of time is made feasible due to the low power consumption of the front-end circuitry (165 μW at 3 V) as well as the proposed intermittent style of operation of the motor. The total sensing system is low power, and its realization is simple and cost-effective, while also offering adequate sensitivity (45 mV/kV/m), making it comparable to the existing works.

Integrated Filter Design for Analog Field Mill Sensor Interface

“…In this application, the motor consumption is approximately 480 mW (@ 3 V), which, even in an intermittent style of operation such as the one suggested in [ 11 ], where the motor would not operate continuously, is still much higher that the power consumption of the filter (404.3 μW) and the sensor interface (1.13 mW) for that matter.…”

“…Therefore, the op-amp employed for the preamplification stage should have very low input bias currents, as well as low input current noise. These requirements were the focal point of [ 11 ], where the op-amp design was optimized to combine low input current and voltage noise, as well as low bias currents, by employing noise minimization techniques and applying them to the sizing process of the MOSFET devices of the op-amp. This class AB amplifier ( Figure 21 ) consists of a PMOS differential pair.…”

“…In [ 5 ], lower power consumption is achieved mainly due to the low power motor used, which in this work was the main power contributor. Therefore, the use of a low-power motor or, alternatively, an intermittent style of operation of the sensor, where the motor is activated for only a small time duration each time, as suggested in [ 11 ], would lead to improved results in terms of power consumption.…”

“…A prototype IC sensor interface has already been developed in a previous work [ 11 ], where emphasis was placed on the noise optimization of the preamplification stage, which consisted of a custom designed integrated operational amplifier. The integrated preamplifier design in [ 11 ] had an input-referred spot noise of 66.7 nV/√Hz at 25.5 Hz which is comparable or, in some cases, outperforms discrete IC op-amps, while simultaneously offering the benefits of integrated design. The synchronous demodulation stage of the proposed interface is designed employing a switch-based multiplier, which allows for full design integration.…”

“…The field mill sensor’s induced signal typically belongs to the low frequency domain (order of tens to hundreds of Hz); therefore, the filter’s passive components should have high values. For the filtering stage of the field mill interface presented in [ 11 ], a multiple feedback narrow bandpass filter was designed, which required the employment of several passive components. In ASICs, bulky passive components are challenging to integrate; thus, several design techniques are adopted to circumvent this issue.…”